Establishment of the identity of Costelytra zealandica (White 1846) (Coleoptera: Scarabeidae: Melolonthinae) a species commonly known as the New Zealand grass grub

White (1846) described Rhisotrogus zealandicus from two syntypes, however no lectotype has since been designated. When the genus Costelytra Given 1952 was described, with Rhisotrogus zealandicus White 1846 as its type species, Given's description of this species was based on 400 specimens collected at different localities in New Zealand as White's syntypes were not available to him. Later, Given (1960) examined one of the syntypes, stating that it was identical to specimens he used to describe C. zealandica, but a lectoype was not designated at this time. So, the aims of this paper are: (i) to provide a detailed description of the external morphology, mouthparts and male genitalia based on the syntypes of R. zealandicus; (ii) to compare these type specimens with the description by Given (1952); (iii) to compare the syntypes to establish if they are conspecific; (iv) to designate an appropriate lectotype and (v) to study a representative series of C. zealandica collected from throughout New Zealand to establish the status of the taxon currently known as C. zealandica. Differences between the syntype specimens, and Given's (1952) description of the New Zealand specimens were found. In addition, White's syntypes are not conspecific. As a result Costelytra giveni n. sp. is established and described to represent the species currently known as the 'New Zealand grass grub'.